Femtosecond optical frequency combs (FOFCs) generated from mode-locked pulsed lasers (MLL) offer a wide spectral bandwidth and ultra-narrow frequency component linewidths while serving as absolute frequency references when phase stabilized. However, due to the wide bandwidth of FOFCs, in some cases each frequency component has nanowatts or less of optical power that might limit ultimate sensitivity and use in spectroscopy. Furthermore, a comb spacing that is given by a repetition rate for a pulsed laser is largely fixed for a given MLL by the physical dimension of the laser cavity and physical reconstruction of the system would be required to change the comb spacing.
The art is receptive to articles and processes that provide optical frequency combs and spectroscopic applications of such combs.